The present invention pertains to DC-to-DC switching power converters, and in particular to DC-to-DC switching power converters fabricated on semiconductor die.
DC-to-DC switching power converters are commonly used to convert one available DC voltage to another DC voltage, often needed for semiconductor die. Such power converters may use one or more electrically controlled switches, such as N-channel or P-channel MOSFET devices. As electronic devices become faster, smaller and more portable, the need for improved electrical efficiency in DC-to-DC converters is becoming more important. Improved electrical efficiency of power converters results in greater overall efficiency of electronic systems, such as microprocessors.
As the operating voltage of microprocessors is reduced, semiconductor die can be operated at higher frequencies and the number of transistors integrated on a single semiconductor die can be increased. Accordingly, the semiconductor die consumes more power from a power supply. The supply paths carrying current to a semiconductor die through a circuit board must carry proportionally more current as the voltage level decreases. As a result, the parasitic elements of the current path to a semiconductor die become more pronounced. For example, narrower track widths along with increased current increase series resistance and inductance increasing ripple, power loss and voltage drop. Furthermore, increasing current requires a greater number of package pins and circuit pads for a die which reduces interconnect reliability.
Switching transistors, such as N-channel and P-channel MOSFET devices, for example, which may be used in power converters, have a capacitive gate control input and are turned on by charging the gate capacitance to an appropriate voltage and are turned off by discharging the gate capacitance. Driver circuitry, such as inverting buffers, is inefficient in charging and discharging the gate capacitance, especially when operated at higher frequencies.
Thus there is a general need for an improved power converter suitable for use on semiconductor die. There is also a need for a more efficient power converter that achieves greater efficiency by reducing the amount of energy to charge and discharge the gate capacitance of switching elements that have capacitive gate control inputs. There is also a need for an on-die power converter that reduces the requirements of off-die voltage regulation modules.